This invention relates to a method for the prevention and treatment of atherosclerotic vascular disease (cardiovascular disease); for the prevention and treatment preeclampsia in pregnant women and for hormone replacement therapy in peri- and post-menopausal women, and for the treatment of hypertension in women and men.
Epidemiological data indicate that approximately one half of the deaths in economically developed countries are attributable to a single major cause, viz., cardiovascular disease, including coronary heart disease, stroke and other forms of vascular disease (Green, A., Bain, C., 1993). The commonest and most lethal form of cardiovascular disease is coronary heart disease. In men, there is a continuous increase in the prevalence of cardiovascular disease after the age of 30-40 years. On the other hand, the rate of cardiovascular disease, especially coronary heart disease, is relatively low among premenopausal women but rises sharply with increasing age, suggesting that sex steroids (estrogens and progesterone) have a protective effect in women. The increased risk of coronary heart disease among women with bilateral oophorectomy further supports the view that steroid hormones may play a protective role with regard to cardiovascular disease.
Cardiovascular disease can be prevented in postmenopausal women by hormone replacement therapy (HRT) with estrogens. The recently performed meta-analysis of 29 studies has demonstrated a reduced cardiovascular disease risk among estrogen users in 23 of these studies (Stampfer et al., 1991). There is also experimental evidence from studies in monkeys that the development of coronary atherosclerosis induced by oophorectomy and diet may be reversed by estrogen supplementation (Adams et al., 1992). On the other hand, there are no effective methods for the prevention of cardiovascular disease in man, since estrogen cannot be used because of side-effects.
The mechanism of the protective effect of female sex hormones is not fully understood. An impact on the lipid profile may be possible. Among postmenopausal women, estrogens reverse the atherogenic changes in lipid profile which is associated with early menopause such as the increase in LDL-cholesterol and serum triglyceride levels and the decrease in HDL-cholesterol. However, new data suggest that both estrogens and progesterone may have a direct effect on the blood vessels. The presence of estrogen and progesterone receptors in arterial endothelial and smooth muscle cells supports the view that sex steroids may have a direct effect on the blood vessels (Lin et al., 1986). It has also been demonstrated that estrogen treatment results in the redistribution of arterial estrogen receptors and in the increase in arterial progesterone receptors in baboons (Lin et al, 1986). Monkey studies suggest that the estrogens may prevent ovariectomy-induced atherosclerosis by inhibiting the uptake and degradation of LDL in the arterial wall (Adams et al., 1992). The effects of estrogens and/or progesterone on arterial tone may also explain some of the beneficial effects of HRT on arterial disease risk. From animal models it is known that estrogens increase uterine blood flow by regulating the vascular tone (Greiss and Anderson, 1970, Ganger et al., 1993). The effects of a sex steroid on the vascular tone suggest that sex steroids may play a role in the pathogenesis of hypertension.
The effects of steroids on the vessels can be mediated by various locally produced hormones including nitric oxide, prostacyclin and endothelin. Both nitric oxide and prostacyclin induce vascular relaxation and inhibit platelet aggregation. On the other hand, endothelin has a strong vasoconstriction effect. Nitric oxide is produced by endothelial cells and is involved in the regulation of vascular tone, platelet aggregation, neurotransmission and immune activation (Furchgott and Zawadzki, 1980; Moncada, Palmer and Higgs, 1991). Nitric oxide, formerly known as EDRF (endothelin-derived relaxing factor) (Furchgott und Zawadzki, 1980; Moncada, Palmer and Higgs, 1991), is synthesized by the oxidative deamination of a guanidino nitrogen of L-arginine by at least three different isoforms of a flavin-containing enzyme, nitric oxide synthase (Moncada, Palmer and Higgs, 1991). Nitric oxide elevates levels of cGMP (1,3,5-cyclic guanosine monophosphate) within the vascular smooth muscle to produce relaxation and to reduce blood vessels tone (Moncada, Palmer and Higgs, 1991).
Prostacyclin is a potent endogenous platelet inhibitory and antithrombogenic substance acting as a local regulator of cell-vessel wall interaction (Willis and Smith 1989). The pharmacological effects of prostacyclin are similar to those of nitric oxide. It is a potent vasodilator which dose-dependently lowers peripheral arterial resistance and blood pressure. The clinical use of prostacyclin is limited due to its chemical instability. Therefore, a prostacyclin analog is preferred, i.e., a prostaglandin derivative with a structure related to prostaglandin which exhibits an effect on the cardiovascular system, e.g., inhibitions of platelet aggregation. Iloprost an cicapristost are stable analogs of prostacyclin. Iloprost was the first compound synthesized that combined the biological profile of prostacyclin with chemical stability (Skuballa et al., 1985). Cicaprost is a metabolically and chemically stable prostacyclin analog which shows high bioavailability and prolonged duration of action (Skuballa et al., 1986). It is highly specific prostacyclin mimic, exhibiting only minor if any effects on organ systems sensitive to other prostaglandins.
There is evidence that prostacyclin analogs exert protective effects on the endothelium. Beneficial effects of cicaprost and iloprost on atherosclerosis were described in animal models. Oral treatment of cholesterol-fed rabbits with cicaprost reduced aortic atheromatous plaque formation and partially prevented hypercholesterolemia-induced impairment of endothelium-dependent relaxation (Braun, M., et al., 1992). In addition, cicaprost reduced hypercholesterolemia-induced platelet and neutrophil hyperactivity in rabbits (Hohfeld et al., 1992). Platelets and leukocytes are believed to contribute to atherogenesis. Furthermore, studies in rabbits showed that oral cicaprost has a beneficial effect on the hypercholesterolemia-induced impairment of coronary vasodilatation (Woditsch I, et al., (1992). Iloprost has been found to protect microvascular arteriolar endothelium from damage by cyclosporin (Burton GA et al., 1992).
These animal studies suggest that prostacyclin analogs alone may be protective against atherosclerosis. There are no experimental or clinical studies with a combination of prostacyclin analogs with a progestin or an estrogen.
Preeclampsia is a pregnancy-specific disease classically defined as the triad of hypertension, pathologic edema and proteinuria normally associated with fetal hypotrophy. The etiology and pathogenesis of this common disease (approximately 10% of all pregnancies) is poorly understood. It is generally believed that preeclampsia is linked to prostacyclin deficiency and increased thromboxane A2 production. The current therapy is restricted to bed rest (mild form), symptomatic medication with antihypertensive drugs and early delivery with attendant risks of operative delivery and iatrogenic prematurity. In preeclampsia, there is a reduced preload, low cardiac output and an elevated after-load which is consistent with a decreased intravascular volume and an increased peripheral vascular resistance. The increased peripheral resistance has been explained by (1) the increased vascular sensitivity to pressor agents and (2) the presence of a vasoactive substance. There is considerable evidence that preeclampsia is associated with an increased sensitivity to the pressor effects of angiotensin 11 and other vasoactive agents (Abdul-Karim 1961, Gant 1973, Gant 1974), platelet activation (Bonnar 1971, Perkins 1979, Giles 1981), and endothelial cell injury (Roberts 1989, Shanklin 1989). The prominent clinical features of preeclampsia, edema and proteinuria are consistent with the loss of endothelial transport function.
Preeclampsia is often considered as an acute form of atherosclerosis. The spiral arteries that perfuse the intervillous space of normal placenta undergo extensive morphological changes during normal pregnancy, viz., a fourfold increase in diameter and a loss of their muscular and elastic components (Robertson 1986). These changes allow for an approximate tenfold increase in uterine blood flow that occurs during normal gestation. These changes are absent in preeclampsia (Robertson 1986) so that the intramyometrial segments of the spiral arteries are unable to dilate. In addition, the basal arteries and myometrial segments of spiral arteries in the preeclamptic placenta demonstrate characteristic lesions which have been called xe2x80x9cacute atherosisxe2x80x9d (Roberts 1989). In acute atherosis of the preeclampsia uterus there is an endothelial cell injury, a focal interruption of the basement membrane, platelet deposition lipoid necrosis of muscle cells (foam cells), (a result of chronic hypoxia and/or cytotoxins), mural thrombi and fibrinoid necrosis (Robertson 1967, DeWolf 1980, Roberts 1989), effects very similar to those seen in atherosclerotic vascular disease.
There is also evidence that prostacyclin production is decreased in preeclampsia. In a normal pregnancy there is an approximately 5-10-fold increase in prostacyclin production compared to the non-pregnant state (Goodman 1982, Walsh 1985, Fitzgerald 1,987). In contrast, there is a decreased production of prostacyclin in maternal, placental and umbilical cord vessels and in placental cotyledons (Remuzzi 1980, Makila 1984, Walsh 1985) in preeclampsia. An imbalance in the ratio of thromboxane A2 to prostacyclin in preeclampsia has been proposed as a major pathological mechanism in preeclampsia (Walsh 1988, Fitzgerald 1987, Friedman 1988). Other experimental studies (unreported) in pregnant rats and guinea pigs indicate that nitric oxide deficiency is the primary event in preeclampsia. Inhibition of nitric oxide synthesis during pregnancy with L-NAME caused the classical symptoms hypertension, proteinuria and fetal growth retardation.
Prostacyclin is available as a stable freeze-dried preparation, viz., epoprostenol, for intravenous administration to man. A major limitation of epoprostenol is the need to administer it parenterally, the steep dose-response relationship for both platelet inhibition and the appearance of side effects, and its short duration of action (Moran and Fitzgerald 1994; Vane 1993). The marked fall in systemic blood pressure, especially associated with the use of epoprostenol, or intravenous iloprost, is why the use of prostacyclin and its analogs has not gained widespread use in the management of cardiovascular disorders (Vane 1993).
There have been attempts to treat preeclampsia with prostacyclin. Prostacyclin consistently relaxes placental blood vessels when tested in vitro (Glance 1986, Howard 1986, Maigaard 1986). However, when tested in vivo, infusion of prostacyclin did not result in the increase in placental perfusion in sheep (Phernetton 1979, Rankin 1979, Landauer 1985) and humans (Husslein 1985). Moreover, studies in the sheep model have also demonstrated that prostacyclin infusion leads to a decrease of placental perfusion with resulting detrimental effects on the fetus.
When it became evident that there exists an imbalance of increased thromboxane and decreased prostacyclin production in preeclampsia, some investigators attempted to treat this disease by means of a constant i.v. infusion of prostacyclin. There are 3 reports on 7 women with severe preeclampsia who were treated with prostacyclin (4-8 ng/kg/min, 5 h to 11 days) after failure of conventional medication (Fidler 1980, Lewis 1981, Belch 1985). In all women, there was a rapid decrease in blood pressure during prostacyclin infusion. The clinical outcome of these studies was poor. All babies were delivered prematurely by cesarean section and only 4/7 babies survived. Fetal bradycardia was observed during treatment and two fetuses died during prostacyclin infusion. The prostacyclin treatment caused a steal phenomenon in these studies and actually decreased uteroplacental blood flow. This explanation is supported by a study of prostacyclin effects in 2 cases of severe early-onset fetal growth retardation. Intravenous prostacyclin was administered in an attempt to promote fetal growth and thus prolong pregnancy. This attempt was unsuccessful and resulted in intrauterine death in each case. In this report the infusion rate of 4 ng/kg/min. was limited by maternal side effects (Steel and Pearce 1988).
These observations indicate that treatment of already established preeclampsia with high-dose prostacyclin is an ineffective and risky strategy. On the other hand, there are no effective methods for the prevention of preeclampsia. Aspirin, when given to inhibit prostaglandin synthesis in relatively low doses, is thought to predominantly suppress the platelet thromboxane A2 production with little inhibition of the vascular prostacyclin production (Massoti 1979). Therefore, low-dose aspirin was proposed for the prevention of preeclampsia. The results of the recently published multicentric study are disappointing, and low-dose aspirin is currently not recommended for the prevention of preeclampsia (CLASP Collaborative Group, 1994). Thus there is need for an effective and safe method of prevention and treatment of preeclampsia.
The unexpected results of the studies described below indicate that the response of blood vessels to prostacyclins and subsequent blood pressure lowering effect is controlled by progesterone. Treatment of pregnant rats with the nitric oxide inhibitor (L-NAME) produces signs and symptoms of preeclampsia (e.g., hypertension, fetal retardation and proteinureaxe2x80x94the classical triad of preeclampsia). These symptoms are related to the decrease in vascular resistance and placental perfusion. In the rat model of preeclampsia (inhibition of nitric oxide synthesis with L-NAME), the blood pressure-lowering effects of cicaprost and iloprost are greater in late pregnancy when progesterone levels are elevated in pregnant rats. Post-partum, when progesterone blood concentrations decrease, there is a rapid increase in blood pressure in animals treated with L-NAME and cicaprost or iloprost. Injection of a progesterone receptor agonist R5020 (promegestone) restores the efficacy of iloprost/cicaprost to lower blood pressure. In addition progesterone partially lowers blood pressure in L-NAME-treated male rats and the antiprogestin RU 486 elevates blood pressure in this model. Thus, the condition of pregnancy and the progestin treatment highly increase the responsiveness of blood vessels to exogenous prostacyclin. The increased response of blood vessels results in the lowering of the effective dose of prostacyclin analogs and subsequently in the reduction of side effects. The treatment of preeclamptic rats with a combination of prostacyclin and a progestin is thus highly effective in lowering blood pressure and fetal mortality and in reversing fetal growth retardation.
A prostacyclin analog in combination with a progestational agent reverses the blood pressure increase induced by the inhibition of nitric oxide. Thus, prostacyclin in combination with progesterone can fully compensate the nitric oxide deficiency. These observations indicate that both the prostacyclin and nitric oxide systems are complementary (and exchangeable) with regard to blood pressure control.
Preeclampsia is a well known model of atherosclerosis as the decrease in placental is accompanied by increased fibrin deposition in placental vessels and increased thrombus formation. Therefore, this regimen is also effective in preventing and treatment of atherosclerotic disease in both female and male mammals.
It is well known that estrogen up-regulates the progesterone receptors in a variety of target organs. Therefore, concurrent estrogen administration with a progestin is preferred.
It is an object of the Invention to provide a method for the prevention and treatment of atherosclerotic vascular disease (cardiovascular disease) in both female and male mammals, with a combination of prostacyclin or a stable analog thereof, e.g., iloprost and cicaprost, with a progestogen and/or estrogen.
It is a further object to provide a method for hormone replacement therapy (HRT) in the peri- and post-menopausal female using an estrogenic agent in combination with prostacyclin or a stable analog thereof.
It is another object to provide a method for hormone replacement therapy (HRT) in the peri- and post-menopausal female using a combination of an estrogenic agent and a progestin agent with prostacyclin or a stable analog thereof.
It is another object to provide such a method in which a progestin and/or estrogen is used in combination with prostacyclin or a stable analog thereof for the prevention and treatment of preeclampsia in pregnant mammals.
It is another object to provide such a method in which an progestin and/or estrogen is used in combination with prostacyclin or a stable analog thereof, e.g., iloprost and cicaprost, for the treatment of hypertension, both in female and male mammals.
A further object is the provision of pharmaceutical compositions useful in practicing the methods of this invention.
Other objects will be apparent to those skilled in the art to which this invention pertains.
In a method aspect, this invention relates to a method of preventing and treating atherosclerotic vascular disease (cardiovascular disease) in both female and male mammals, including the treatment of preeclampsia in a pregnant female mammal and treating hypertension in both female and male mammals, which comprises administering to a subject manifesting the symptoms thereof (a) a prostacyclin or a prostacyclin analog, e.g., in an amount bioequivalentto 0.1-10 ng/kg/min of prostacyclin intravenously, and (b) one or both of a progestin and an estrogen, e.g., an amount of estrogen bioequivalent to approximately 2 mg per day of estradiol and an amount of progestin bioequivalent to 50-300 mg of injected progesterone, effective to ameliorate the symptoms.
In a product aspect, this invention relates to a pharmaceutical composition comprising at least one of the prostacyclin analog in combination with one or more of an estrogen and/or progestin with the amount of the estrogen being bioequivalent to about 2 mg of estradiol (e.g. xe2x80x9cProgynova, R.xe2x80x9d, Schering, A. G.) with the amount of the progestin being bioequivalent to 50-300 mg of injected progesterone.
Other aspects will be apparent to those skilled in the art to which this invention pertains.
The compositions of this invention can be used to prevent and treat atherosclerotic vascular disease (cardiovascular disease) and treat hypertension in both female and male mammals, preferably human, and used for hormone replacement therapy in peri- and postmenopausal women. The methods of this invention can prevent and treat preeclampsia in pregnant mammals, e.g., a human who is manifesting the symptoms thereof or who is a high risk candidate for doing so, e g., as determined by the progress of a present or previous pregnancy.
Since the female sex steroids (progesterone and estrogens) act synergistically with prostacyclin and its analogs, a combination of a prostacyclin analogs with a progestin, an estrogen or both an estrogen and a progestin, is employed. A synergistic effect is achieved when a progestational and/or estrogenic agent is administered concurrently with the prostacyclin or prostacyclin analog.
Thus, the method aspect of this invention and the pharmaceutical composition aspect of this invention employs prostacyclin or a prostacyclin analog and one or more of an estrogen (e.g, estradiol valerate, conjugated equine estrogens, 17xcex2-estradiol, estriol or ethinyl estradiol such as xe2x80x9cPyrgynova Rxe2x80x9d, Schering, A. G.) and a progestin (e.g., progesterone, dydrogesterone, medroxyprogesterone, norethisterone, levonogestrel, norgestrel or gestoden).
Examples of combinations of prostacyclin analogs which are administered concurrently with a progestin and/or an estrogen are: prostacyclin (epoprostenol), iloprost, cicaprost. The following are typical oral dosage ranges active agents of the estrogen and progestin with a prostacyclin analog:
Prostacyclin: Iloprost, 10-1000 xcexcg/patient; twice-a-day orally; Cicaprost, 1-100 pg/patient; twice-a-day orally.
Estrogens: a daily dose bioequivalent to about 1 to 2 mg per day, eg., xe2x80x9cPremarin Rxe2x80x9d (Wyeth-Ayerst), 0.625 mg/day; estradiol valerate, 50 U9/day transdermally, vaginal estradiol creams, 1.25 mg/day and vaginal estradiol rings, 0.2 mg/day.
Progestins: A daily dose bioequivalent to 50-300 mg of progesterone/day, e.g., an injectable suspension of medroxyprogesterone acetate, to provide a weekly dose of thereof of 100-1000 mg in tablets or dragees providing an oral dose thereof of 5-10 mg/day, an injectable solution of hydroxyprogesterone caproate which provides a weekly dose of 250-500 mg; tablets, capsules or dragees of northindrone acetate which provide a daily dose of 5-20 mg.
Examples of estrogens and progestins are listed below. (Oral xe2x80x9cnaturalxe2x80x9d estrogens used in hormone replacement therapy currently available in the UK.)
Commercially available combination calendar packs or hormone replacement therapy include xe2x80x9cEstrapakxe2x80x9d, xe2x80x9cPrempak-Cxe2x80x9d, xe2x80x9cTrisequensxe2x80x9d, xe2x80x9cTrisequens fortexe2x80x9d and xe2x80x9cCycloprogynovaxe2x80x9d. The following are illustrative compositions of such products: Oestradiol 50 mg per day (28 days, 8 patches); Conjugated equine estrogens 0.625 mg per day (28 days); Oestradiol valerate 2 mg per day (11 days); Oestradiol valerate 2 mg per day; Norgestrel 0.5 mg per day (12 days); Norgestrel 0.15 mg per day (12 days); Conjugated equine estrogens 1.25 mg per day (28 days); Norethisterone acetate 1 mg per day (10 days); Oestradiol 1 mg per day+oestriol 0.5 mg per day (6 days); Norethisterone acetate 1 mg per day (10 days); Oestradiol 1 mg per day+oestriol 0.5 mg per day (6 days); Oestradiol valerate 1 mg per day (21 days); Levonorgestrel 0.25 mg per day (10 days); Oestradiol valerate 2 mg per day (21 days); Levonorgestrel 0,5 mg per day (10 days).
Daily doses of progestogen to be taken for 12 days per month by patients receiving oral or transdermal estrogens:
Norethisterone, 0.7-2.5 mg per day; medroxyprogesterone acetate, 10 mg per day; norgestrel, 150 mg per day; and dydrogesterone, 10-20 mg per day.
The pharmacologically active agents employed in this invention can be administered in admixture with conventional excipients, i.e., pharmaceutically acceptable liquid, semi-liquid or solid organic or inorganic carriers suitable, e.g., for parental or enteral application and which do not deleteriously react with the active compound in admixture therewith. Suitable pharmaceutically acceptable carriers include but are not limited to water, salt solutions, alcohols, vegetable oils, polyethylene glycols, gelatin, lactose, amylose, magnesium stearate, talc, silicic acid, vicious paraffin, perfume oil, fatty acid monoglycerides and diglycerides, pentaerythritol fatty acid esters, hydroxy methylcellulose, polyvinyl pyrrolidone, etc.
The pharmaceutical preparations can be sterilized and if desired mixed with auxiliary agents, e.g., lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salts for influencing osmotic pressure, buffers, coloring, flavoring and/or aromatic substances and the like which do not deleteriously react with the active compounds.
For parental application, particularly suitable are solutions, preferably oily or aqueous solutions, as well as suspensions, emulsions, or implants, including suppositories and transdermal patches. Ampoules are convenient unit dosages.
In a preferred aspect, the composition of this invention is adapted for ingestion.
For enteral application, particularly suitable are unit dosage forms, e.g., tablets, dragees or capsules having talc and/or a carbohydrate carrier or binder or the like, the carrier preferably being lactose and/or corn starch and/or potato starch; particulate solids, e.g., granules; and liquids and semi-liquids, e.g., syrups and elixirs or the like, wherein a sweetened vehicle is employed. Sustained release compositions can be formulated including those wherein the active compound is protected with differentially degradable coatings, e.g., by microencapsulation, multiple coatings, etc.
Suitable for oral administration are, inter alia, tablets, dragees, capsules, pills, granules, suspensions and solutions. Each unit dose, e.g., each tablespoon of liquid or each tablet, or dragee contains, for example, 5-5000 mg of each active agent.
Solutions for parenteral administration contain, for example, 0.01-1% of each active agent in an aqueous or alcoholic solution.
The prostacyclin analog can be administered as an admixture with an estrogen and/or progestin and any other optional active agent or as a separate unit dosage form, either simultaneously therewith or at different times during the day from each other.
The combination of active agents is preferably administered at least once daily (unless administered in a dosage form which delivers the active agents continuously) and more preferably several times daily, e.g., in 2 to 6 divided doses.
In humans, both a prostacyclin analogue and progesterone (or bioequivalent of another progestin) should be given in a ratio which produces blood plasma levels of about 30-100 xcexcmolar progesterone and 500 to 1000 nmolar of estradiol.